Dr. Jeff Hersh: Options in high-risk pregnancies

Dr. Jeff Hersh

Tuesday

Dec 28, 2010 at 12:01 AMDec 28, 2010 at 2:47 PM

Q: My cousin lost her pregnancy during her second trimester a couple of years ago. She is pregnant again and they are considering sewing her cervix closed. Will this help prevent problems with this birth?

Q: My cousin lost her pregnancy during her second trimester a couple of years ago. She is pregnant again and they are considering sewing her cervix closed. Will this help prevent problems with this birth?

A: A miscarriage is the spontaneous loss of a fetus prior to 20 weeks gestation; most are thought to be due to fetal abnormalities. Spontaneous fetal loss between 20 and 24 weeks gestation is termed a stillbirth. Between 24 weeks, when the fetus is considered potentially viable, and 37 weeks gestation (normal gestation is considered 37 to 40 weeks) a live birth is considered premature; 12 percent of births in the United States are premature. It is not well understood why these occur.

Ensure they have adequate nutrition (prenatal vitamins are usually recommended).

Maintain normal body mass.

Wait at least six months between pregnancies.

Stop smoking.

Infections, such as urine infections, should be treated during pregnancy. Women at high risk of premature labor should avoid excessive stress and over-long working hours, as well as shift work. They should also try to avoid excessive physical exertion and prolonged standing.

Many -- likely most -- premature births are due to inflammation-mediated biochemical changes that lead to early cervical ripening (where the cervix becomes softer and can easily distend). This is supported by evidence that progesterone treatment benefits some women with a history of spontaneous preterm births.

Some percentage of premature births are due to an incompetent cervix, where the cervix is weak and begins to open too soon. However, it is not known how to determine when this may be the case. It is thought that women with a history of multiple painless second trimester premature births may be more likely to have an incompetent cervix.

A short cervix noted on ultrasound (the cervix is usually over 25 centimeters long -- about 10 inches -- until after 32 weeks gestation), especially if it is very short early in the pregnancy (for example, under 10 cm by 20 to 24 weeks gestation), also raises the suspicion of cervical incompetence.

Cervical cerclage is a surgical procedure that uses sutures, wires or special surgical tape to increase the mechanical closure strength of a woman's cervix. Although clinical trial evidence is limited, it is thought that carefully selected women may benefit from this procedure to prevent premature delivery; a baby's prognosis is much improved the closer to full term they are carried.

Cervical cerclage is usually done as an outpatient or overnight admission procedure. Most cerclages are done trans-vaginally, although a trans-abdominal procedure may be indicated for certain patients. Mechanical closure of the cervix is achieved in up to 90 percent or more of cerclage procedures.

Overall, about 5 percent of cerclage procedures have some complication, such as infection (more common if the cervix is significantly dilated), rupture of the fetal membranes (more common if the membranes are protruding through the cervical opening), uterine contractions, migration of the sutures (sometimes requiring a repeat procedure), amniotic fluid leakage and/or abdominal pain.

In women with a high likelihood of cervical incompetence who are felt to be at high risk of another premature birth, an elective cerclage may be done at 12 to 14 weeks gestation (fetal loss due to fetal abnormalities usually occurs prior to then). An urgent cerclage may be considered in women felt to be at risk who are noted to have a significantly shortened cervix early in their pregnancy, typically before 24 weeks gestation.

Cerclage is not usually done between 24 and 28 weeks gestation since there may be high neonatal complications (even death) during this period. It is also not usually done after 28 weeks gestation since the fetus is then considered viable and other methods to delay birth (such as tocolytic medications to suppress contractions) are usually employed.

The cerclage is usually removed at 37 weeks gestation, the earliest "normal" duration for a pregnancy. If there is premature rupture of membranes after 32 weeks gestation many obstetricians will remove the cerclage to allow the delivery to progress, since babies delivered after 32 weeks gestation have an overall good prognosis.

An experienced obstetrician should be consulted to help decide the best options to manage women with high-risk pregnancies.